A frequent reader of Luke Surl would never seriously (I think you are serious, I might be wrong) call this comic racist. Luke uses characters of all races all the time. Over-PC-ness leading to not portraying minorities in any negative way is racist, the comic is not.

In actuality, I always choose the colour of my characters literally for colour, usually to contrast the background. In the image above having the left-hand chef as white would make the overall image too bright and I don’t think it would have been as good asthetically.